1. Field of the Invention
The present invention relates to a travel lane boundary line detection apparatus.
2. Description of the Related Art
As conventional travel lane boundary line detection apparatuses, Japanese Patent Application Laid-open No. 2013-120458, for example, discloses a road shape estimation apparatus for detecting plural edge lines from an image of a road surface in a travel region in which composite lines formed including travel lane boundary lines (for example, solid white lines) and auxiliary lines (for example, dotted white lines) are drawn on the travel road surface, coupling one or more of the edge lines to create composite edge lines, and determining road shape parameters including an offset in a lateral direction of a camera that has picked up the road surface and a road width based on the information of the inside composite edge line nearest to the central portion of a road. The road shape estimation apparatus determines a correction amount based on the distance between the inside composite edge line and an outside composite edge line, and corrects the offset in the lateral direction and the road width using the correction amount. With the operation, the road shape estimation apparatus can accurately estimate a road shape from the image of the road surface without being affected by auxiliary lines due to decreased resolution even in a travel road on which the auxiliary lines are painted in parallel with a travel lane marking.
Incidentally, in the road shape estimation apparatus described in Japanese Patent Application Laid-open No. 2013-120458, when the correction has been carried out to the offset in the lateral direction and to the road width of the road shape parameters that are based on the information of the inside composite edge line nearest to the center of a road at, for example, a switching point where the composite lines are switched with single lines formed by the travel lane boundary lines, there is a fear that the parameters representing the travel lane boundary lines in the travel region of the single lines are excessively offset to the outside of an actual road. Thus, the road shape estimation apparatus has a room for improvement in the point of estimation of the parameters for representing more appropriate travel lane boundary lines.